A process for fabricating a semiconductor device has dealt with the issue of cleanliness required in such processes by forming the whole plant for applying various treatments to a wafer into a clean room. However, because the diameter of a wafer is increased, the above method becomes a problem in cost to obtain the high clean environment. Means for securing a mini-environment (very small environment) space keeping a high cleaning degree has been taken for various treating apparatuses in these several years.
Specifically, instead of increasing the cleaning degree of the entire factory, only insides of treating apparatuses and inside of a storing container (hereafter referred to as pod) during movement between them in a manufacturing process are kept at a high cleaning degree. This pod is referred to as FOUP as described above. Thus, by bringing a small space into a high cleaning degree, the advantage same as the case of forming the whole plant into a clean room is obtained, equipment investment and maintenance cost are reduced, and an efficient production process is realized.
A semiconductor treating apparatus or the like dealing with the so-called mini-environment system actually used is briefly described below. FIG. 15 shows the whole of a semiconductor wafer treating apparatus 50. The semiconductor wafer treating apparatus 50 is mainly constituted of a load port portion 51, a conveying chamber 52, and treating chamber 59. Junctions therebetween are comparted by a load-port-side compartment 55a and cover 58a, and treating-chamber-side compartment 55b and cover 58b. In the conveying chamber 52 in the semiconductor wafer treating apparatus 50, to discharge dust and keep a high cleaning degree, an air flow is generated from the upper portion toward the lower portion of the chamber 52 by a fan (not illustrated) set on the chamber. Thus, dust is continuously discharged toward the lower side.
On the load port portion 51, a pod 2 serving as a container for storing a silicon wafer (hereafter referred to as wafer) or the like is set on a pedestal 53. As previously described, the inside of the conveying chamber 52 is kept at a high cleaning degree in order to treat a wafer 1 and moreover, a robot arm 54 is set to the inside. This robot arm 54 moves the wafer between the inside of the pod 2 and the inside of the treating chamber 59. Various mechanisms for forming a thin film on the surface of the wafer or the like and treating the thin film are generally included in the treating chamber 59 but description of these configurations is omitted because they are not directly related to the present invention.
The pod 2 has a space for storing the wafer 1 which is a product to be treated at the inside and includes a boxy body portion 2a having an opening on any face and a lid 4 for closing the opening. A shelf having a plurality of stages for overlapping wafers 1 in one direction is set in the body portion 2a and wafers 1 mounted on the stages are housed in the pod 2 by making intervals between the wafers 1 constant. In the case of the example shown here, the direction for overlapping the wafers 1 is vertical. An opening 10 is formed at the load port portion 51-side of the conveying chamber 52. The opening 10 is set to a position facing the opening of the pod 2 when the pod 2 is set on the load port portion 51 so as to be close to the opening 10. An opener 3 to be described later is also set nearby the opening 10 in the conveying chamber 52.
FIGS. 16A and 16B show a side sectional view obtained by enlarging the opener-3 portion in a conventional apparatus and a front view viewing the opener 3 from the conveying chamber-52 side. FIG. 17 shows a schematic view of the side cross section of a state in which the lid 4 is removed from the pod 2 by using the opener 3. The opener 3 has a door 6 and a door arm 42. A fixed member 46 is set to the door 6 and the door 6 is rotatably connected to one end of the door arm 42 through the fixed member 46. The other end of the door arm 42 is supported to the front end of a rod 37 which is a part of a pneumatic cylinder 31 rotatably through a pivot 40.
A through-hole is formed between one end of and the other end of the door arm 42. A fulcrum 41 is constituted by the fact that a not-illustrated pin passes through the through-hole and a hole of a fixed portion 39 fixed to a support member 60 of a movable portion 56 for vertically moving the opener 3. Therefore, the door arm 42 becomes rotatable about the fulcrum 41 in accordance with the telescopic motion of the rod 37 due to driving by the cylinder 31. The fulcrum 41 of the door arm 42 is fixed to the support member 60 set to the movable portion 56 which can be vertically moved. The door 6 has holding ports 11a and 11b and is able to hold the lid 4 of the pod 2 by means of vacuum attraction.
To treat the wafer 1 with these configurations, the pod 2 is set on the pedestal 53 so as to be close to the conveying-chamber opening 10 to hold the lid 4 by the door 6. Then, when contracting the rod of the cylinder 31, the door arm 42 moves so as to leave the conveying-chamber opening 10 about the fulcrum 41. The door 6 rotates together with the lid 4 to remove the lid 4 from the pod 2 in accordance with the above operation. The state is shown in FIG. 17. Thereafter, the movable portion 56 is lowered to convey the lid 4 up to a predetermined evacuation position.
The inside of the pod 2 while housing a wafer or the like is filled with dry nitrogen or the like controlled at a high cleaning degree to prevent contaminant, oxidizing gas or the like from entering the pod. However, because the pod also houses a wafer after passing through the treating chamber, a case is considered in which contaminant or the like attaches to the wafer in the treating chamber or the like and this is brought into the pod. When the contaminant or the like is brought into the next treating chamber, a case may occur in which a desired wafer treatment which should be originally performed may not be performed when passing through the treating chamber. Therefore, when moving the wafer from the pod to the conveying chamber, it is necessary to remove the contaminant or the like.
In the case of a conventional FOUP, to deal with the above request, an inlet hole for introducing purging gas into the pod and an outlet hole for discharging the purging gas are formed at the bottom of the FOUP. These inlet and outlet holes are respectively connected with an inlet hole and outlet hole for purging gas set on a support pedestal on which the pod is mounted. As an actual operation, a high-pressure gas controlled at a high cleaning degree is introduced into the pod from the support pedestal side through these inlet holes. At the same time, the gas and contaminant present in the pod are discharged to the outside of the pod through these outlet holes. Contaminant or the like brought into the pod has been removed in accordance with the operation.
However, only by introducing a high-pressure gas from the bottom of the pod, it is considered that a gas flow mainly passes through a portion nearby the outer periphery of a wafer through which gas easily passes. Therefore, it is considered that it is difficult to pass a gas having a sufficient flow rate through the upper and lower faces of individual wafers held by keeping very small intervals. However, contaminant or the like is mainly attached to the upper face or lower face of a wafer and therefore, it is considered that it is difficult to sufficiently remove contaminant or the like by a conventional method.
To securely remove the contaminant from a wafer, the method disclosed in Japanese Patent Application Laid-Open No. 2003-45933 is proposed. In the case of this method, a space for housing an opener is formed separately from a conveying chamber. The space has a gas supply port at the front upper portion of the opening of a pod. Clean gas is supplied into the pod from the gas supply port and the clean gas circulating through the pod and discharged to the space from the bottom of the pod is exhausted from the bottom of the space. By using the above configuration and thereby circulating the clean gas through the pod, it is possible to more securely remove contaminant or the like, compared with the case of the conventional method.
Moreover, Japanese Patent Application Laid-Open No. 11-251422 discloses a method for introducing clean gas between wafers held in a pod. In the case of this method, a gas introducing channel and a gas discharging channel communicating with groove portions for supporting wafers are formed in the pod. By spraying clean gas on the surface of each wafer through the gas introducing channel and discharging the clean gas containing contaminant or the like through the gas discharging channel, it is possible to more securely remove the contaminant.
In the case of the method disclosed in Japanese Patent Application Laid-Open No. 2003-45933, an effect can be expected on reduction of humidity and of an oxidizing gas in a pad and prevention of organic contamination to a certain extent. However, it is considered that it is also difficult to effectively replace the gas present between wafers held by keeping very small spaces. Therefore, it is considered that it is also difficult to obtain an effect for removing contaminant attached to the upper and lower faces of a wafer.
According to the method disclosed in Japanese Patent Application Laid-Open No. 11-251422, it is considered that it is possible to remove contaminant attached to upper and lower faces of a wafer. However, it is considered that it is difficult to keep the inside diameter of a gas introducing channel at a large value from the viewpoint of an actual configuration. Therefore, a difference occurs in a gas pressures introduced on the surface of a wafer or times introduced at a predetermined pressure at the upstream side and downstream side of the channel and it is considered that the contaminant removal effect depends on a wafer holding position.
Moreover, arrangement of a support pedestal, pod shape, and holes for supplying and discharging clean gas for purging inside of pod is almost standardized in the semiconductor manufacturing business circle. Therefore, the pod disclosed in Japanese Patent Application Laid-Open No. 11-251422 requiring a configuration different from the standard has a problem that the pod cannot be shared with a support pedestal generally used at present.